The present invention relates generally to gas turbine engines, and more particularly to a circumferential valve of a gas turbine engine.
A gas turbine engine typically includes a high pressure spool, a combustion system and a low pressure spool disposed within an engine case to form a generally axial, serial flow path about the engine centerline. The high pressure spool includes a high pressure turbine, a high pressure shaft extending axially forward from the high pressure turbine, and a high pressure compressor connected to a forward end of the high pressure shaft. The low pressure spool includes a low pressure turbine, which is disposed downstream of the high pressure turbine, a low pressure shaft, which typically extends coaxially through the high pressure shaft, and a low pressure compressor connected to a forward end of the low pressure shaft, forward of the high pressure compressor. The combustion system is disposed between the high pressure compressor and the high pressure turbine and receives compressed air from the compressors and fuel provided by a fuel injection system. A combustion process is carried out within the combustion system to produce high energy gases to produce thrust and turn the high and low pressure turbines, which drive the compressors to sustain the combustion process.
During start-up of a gas turbine engine, the low pressure turbine is not providing power to turn the low pressure compressor. Therefore, the low pressure compressor includes a valve to vent the air from the low pressure compressor so that rotating the low pressure compressor is easier. In addition, during acceleration and deceleration, the output of the low pressure compressor may need to be vented in order to maintain pressure balance between the low and high pressure compressors to prevent stalling thereof. (These are only two examples of why a valve is placed in the low pressure compressor.) The air from the low pressure compressor escapes through ports in the body, but flow through these ports must be prevented to allow for normal operation of the gas turbine engine.